The present invention evolved from continuing development efforts pertaining to subject matter disclosed in my application Ser. No. 216,872, filed Dec. 15, 1980, and now issued as U.S. Pat. No. 4,330,868. This referenced patent discloses coupling circuitry for the LO signal utilizing a Lange-type 90.degree. quadrature hybrid 3 dB coupler comprised of a plurality of interdigitated striplines, for example as described in "Interdigitated Strip-Line Quadrature Hybrid", Julius Lange, 1969 International Microwave Symposium, Dallas, Tex., May 5-7, IEEE Cat. No. 69 c 6, pp. 10-13.
The present invention relates to improvements in the coupling circuitry combination providing significant cost reduction. The invention provides a microstrip circuit layout combination which affords the desired coupling and eliminates the Lange-type interdigitated coupler which is more costly to implement. The invention further relates to additional improvements in microstrip circuit layout to further improve the cost effectiveness of the overall circuit.